Have you been annoyed by the "SmartSync" battery-saving feature found on HTC's newest phones? If you're not familiar with this aspect of Sense 4.0, that might make, well, sense. HTC has been fairly quiet about how exactly its battery optimizations in Sense work, but SmartSync is a big part of it, especially when it comes to saving juice overnight.
All Sense 4 phones (HTC One X, XL, S, V and EVO 4G LTE) utilize this feature to reduce battery consumption in the wee-hours, specifically from 12AM to 7AM. After 15 minutes of inactivity (no emails, screen off, etc.) in this time frame, Sense 4 phones go into "SmartSync" mode - deactivating all data connections and turning off sync.